Process for producing microbial transglutaminase

ABSTRACT

Disclosed are a protein having a transglutaminase activity, which comprises a sequence ranging from serine residue at the second position to proline residue at the 331st position in an amino acid sequence represented by SEQ ID No. 1 wherein the N-terminal amino acid of the protein corresponds to serine residue at the second position of SEQ ID No. 1, a DNA encoding the protein, a transformant having the DNA, and a process for producing a protein having a transglutaminase activity, which comprises the steps of culturing the transformant in a medium. The protein can be produced in a large amount with the transformant using a host such as  E. coli.

This application is a Continuation of U.S. application Ser. No. 09/109,063, filed on Jul. 2, 1998, now U.S. Pat. No. 6,013,498.

BACKGROUND OF THE INVENTION

The present invention relates to a protein having a transglutaminase activity, DNA which encodes for the protein, and a process for producing the protein. In particularly, the present invention relates to a process for producing a protein having a transglutaminase activity by a genetic engineering technique.

Transglutaminase is an enzyme which catalyzes the acyl transfer reaction of a γ-carboxyamido group in a peptide chain of a protein. When such an enzyme react with the protein, a reaction of an ε-(γ-Glu)-Lys forming reaction or substitution reaction of Gln with Glu by the deamidation of Glu can occur.

The transglutaminase is used for the production of gelled foods such as jellies, yogurts, cheeses, gelled cosmetics, etc. and also for improving the quality of meats [see Japanese Patent Publication for Opposition Purpose (hereinafter referred to as “J. P. KOKOKU”) No. Hei 1-50382]. The transglutaminase is also used for the production of a material for microcapsules having a high thermal stability and a carrier for an immobilized enzyme. The transglutaminase is thus industrially very useful.

As for transglutaminases, those derived from animals and those derived from microorganisms (microbial transglutaminase; hereinafter referred to as “MTG”) have been known hitherto.

The transglutaminases derived from animals are calcium ion-dependent enzymes which are distributed in organs, skins and bloods of animals. They are, for example, guinea pig liver transglutaminase [K. Ikura et al., Biochemistry 27, 2898 (1988)], human epidermis keratin cell transglutaminase [M. A. Philips et al., Proc. Natl. Acad. Sci. USA 87, 9333 (1990)] and human blood coagulation factor XIII (A. Ichinose et al., Biochemistry 25, 6900 (1990)].

As for the transglutaminases derived from microorganisms, those independent on calcium were obtained from microorganisms of the genus Streptoverticillium. They are, for example, Streptoverticillium griseocarneum IFO 12776, Streptoverticillium cinnamoneum sub sp. cinnamoneum IFO 12852 and Streptoverticillium mobaraense IFO 13819 [see Japanese Patent Unexamined Published Application (hereinafter referred to as “J. P. KOKAI”) No. Sho 64-27471].

According to the peptide mapping and the results of the analysis of the gene structure, it was found that the primary structure of the transglutaminase produced by the microorganism is not homology with that derived from the animals at all (European Patent publication No. 0 481 504 A1).

Since the transglutaminases (MTG) derived from microorganisms are produced by the culture of the above-described microorganisms followed by the purification, they had problems in the supply amount, efficiency, and the like. It is also tried to produce them by a genetic engineering technique. This technique includes a process which is conducted by the secretion expression of a microorganism such as E. coli, yeast or the like (J. P. KOKAI No. Hei 5-199883), and a process wherein MTG is expressed as an inactive fusion protein inclusion body in E. coli, this inclusion body is solubilized with a protein denaturant, the denaturant is removed and then MTG is reactivated to obtain the active MTG (J. P. KOKAI No. Hei 6-30771).

However, these processes have problems when they are practiced on an industrial scale. Namely, when the secretion by the microorganisms such as E. coli and yeast is employed, the amount of the product is very small; and when MTG is obtained in the form of the inactive fusion protein inclusion body in E. coli, an expensive enzyme is necessitated for the cleavage.

It is known that when a foreign protein is secreted by the genetic engineering method, the amount thereof thus obtained is usually small. On the contrary, it is also known that when the foreign protein is produced in the cell of E. coli, the product is in the form of inert protein inclusion body in many cases although the expressed amount is high. The protein inclusion body must be solubilized with a denaturant, the denaturating agent must be removed and then MTG must be reactivated.

It is already known that in the expression in E. coli, an N-terminal methionine residue in natural protein obtained after the translation of gene is efficiently cleaved with methionine aminopeptidase. However, the N-terminal methionine residue is not always cleaved in an exogenous protein.

Processes proposed hitherto for obtaining a protein free from N-terminal methionine residue include a chemical process wherein a protein having methionine residue at the N-terminal or a fusion protein having a peptide added thereto through methionine residue is produced and then the product is specifically decomposed at the position of methionine residue with cyanogen bromide; and an enzymatic process wherein a recognition sequence of a certain site-specific proteolytic enzyme is inserted between a suitable peptide and an intended peptide to obtain a fusion peptide, and the site-specific hydrolysis is conducted with the enzyme.

However, the former process cannot be employed when the protein sequence contains a methionine residue, and the intended protein might be denatured in the course of the reaction. The latter process cannot be employed when a sequence which is easily broken down is contained in the protein sequence because the yield of the intended protein is reduced. In addition, the use of such a proteolytic enzyme is unsuitable for the production of protein on an industrial scale from the viewpoint of the cost.

Conventional processes for producing MTG have many problems such as supply amount and cost. Namely, in the secretion expression by E. coli, yeast or the like, the expressed amount is disadvantageously very small. In the production of the fusion protein inclusion body in E. coli, it is necessary, for obtaining mature MTG, to cleave the fusion part with restriction protease after the expression. Further, it has been found that since MTG is independent on calcium, the expression of active MTG in the cell of a microorganism is fatal because this enzyme acts on the endoprotein.

Thus, for the utilization of MTG, produced by the gene recombination, on an industrial scale, it is demanded to increase the production of mature MTG free of the fusion part. The present invention has been completed for this purpose. The object of the present invention is to product MTG in a large amount in microorganisms such as E. coli.

When MTG is expressed with recombinant DNA of the present invention, methionine residue is added to the N-terminal of MTG. However, by the addition of the methionine residue to the N-terminal of MTG, there is some possibility wherein problems of the safety such as impartation of antigenicity to MTG occur. It is another problem to be solved by the present invention to produce MTG free of methionine residue corresponding to the initiation codon.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a novel protein having a transglutaminase activity.

Another object of the present invention is to provide a DNA encoding for the novel protein having a transglutaminase activity.

Another object of the present invention is to provide a recombinant DNA encoding for the novel protein having a transglutaminase activity.

Another object of the present invention is to provide a transformant obtained by the transformation with the recombinant DNA.

Another object of the present invention is to provide a process for producing a protein having a transglutaminase activity.

These and other objects of the present invention will be apparent from the following description and examples.

For solving the above-described problems, the inventors have constructed a massive expression system of protein having transglutaminase activity by changing the codon to that for E. coli, or preferably by using a multi-copy vector (pUC19) and a strong promoter (trp promoter).

Since MTG is expressed and secreted in the prepro-form from microorganisms of actinomycetes, the MTG does not have methionine residue corresponding to the initiation codon at the N-terminal, but the protein expressed by the above-described expression method has the methionine residue at the N-terminal thereof. To solve this problem, the inventors have paid attention to the substrate specificity of methionine aminopeptidase of E. coli, and succeeded in obtaining a protein having transglutaminase activity and free from methionine at the N-terminal by expressing the protein in the form free from the aspartic acid residue which is the N-terminal amino acid of MTG. The present invention has been thus completed.

Namely, the present invention provides a protein having a transglutaminase activity, which comprises a sequence ranging from serine residue at the second position to proline residue at the 331st position in an amino acid sequence represented by SEQ ID No. 1 wherein N-terminal amino acid of the protein corresponds to serine residue at the second position of SEQ ID NO: 1.

There is provided a protein which consists of an amino acid sequence of from serine residue at the second position to proline residue at the 331st position in an amino acid sequence of SEQ ID NO: 1.

There is provided a DNA which codes for said proteins.

There is provided a recombinant DNA having said DNA, in particular, a recombinant DNA expressing said DNA.

There is provided a transformant obtained by the transformation with the recombinant DNA.

There is provided a process for producing a protein having a transglutaminase activity, which comprises the steps of culturing the transformant in a medium to produce the protein having a transglutaminase activity and recovering the protein.

Taking the substrate specificity of methionine aminopeptidase into consideration, the process for producing the protein having transglutaminase activity and free of initial methionine is not limited to the removal of the N-terminal aspartic acid.

BRIEF EXPLANATION OF THE DRAWINGS

FIG. 1 shows a construction scheme of MTG expression plasmid pTRPMTG-01.

FIG. 2 shows a construction scheme of MTG expression plasmid pTRPMTG-02.

FIG. 3 is an expansion of SDS-polyacrylamide electrophoresis showing that MTG was expressed.

FIG. 4 shows a construction scheme of MTG expression plasmid pTRPMTG-00.

FIG. 5 shows a construction scheme of plasmid pUCN216D.

FIG. 6 shows a construction scheme of MTG expression plasmid pUCTRPMTG(+)D2.

FIG. 7 shows that GAT corresponding to Aspartic acid residue is deleted.

FIG. 8 shows that N-terminal amino acid is serine.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The proteins having a transglutaminase activity according to the present invention comprise a sequence ranging from serine residue at the second position to proline residue at the 331st position in an amino acid sequence represented by SEQ ID NO: 1 as an essential sequence but the protein may further have an amino acid or amino acids after proline residue at the 331st position. Among these, the preferred is a protein consisting of an amino acid sequence of from serine residue at the second position to proline residue at the 331st position in an amino acid sequence of SEQ ID NO: 1.

In these amino acid sequences, the present invention includes amino acid sequences wherein an amino acid or some amino acids are delete d, substituted or inserted as far as such amino acid sequences have a transglutaminase activity.

The DNA of the present invention encodes the above-mentioned proteins. Among these, the preferred is a DNA wherein a base sequence encoding for Arg at the forth position from the N-terminal amino acid is CGT or CGC, and a base sequence encoding for Val at the fifth position from the N-terminal amino acid is GTT or GTA. Furthermore, the preferred is a DNA wherein a base sequence encoding for the N-terminal amino acid to fifth amino acid, Ser-Asp-Asp-Arg-Val, (SEQ ID NO: 60) has the following sequence.

Ser: TCT or TCC

Asp: GAC or GAT

Asp: GAC or GAT

Arg: CGT or CGC

Val: GTT or GTA

In this case, the preferred is a DNA wherein a base sequence encoding for amino acid sequence of from the N-terminal amino acid to fifth amino acid, Ser-Asp-Asp-Arg-Val, (SEQ ID NO: 60) has the sequence TCT-GAC-GAT-CGT-GTT. (SEQ ID NO: 61)

Furthermore, the preferred is a DNA wherein a base sequence encoding for amino acid sequence of from sixth amino acid to ninth amino acid from the N-terminal amino acid, Thr-Pro-Pro-Ala, has the following sequence.

Thr: ACT or ACC

Pro: CCA or CCG

Pro: CCA or CCG

Ala: GCT or GCA

Furthermore, the preferred is a DNA comprising a sequence ranging from thymine base at the fourth position to guanine base at the 993rd position in the base sequence of SEQ ID NO: 2. In this case, more preferred is a DNA consisting of a sequence ranging from thymine base at the fourth position to guanine base at the 993rd position in the base sequence of SEQ ID NO: 2.

In the DNA sequences mentioned above, nucleic acids encoding an amino acid or some amino acids may be deleted, substituted or inserted as far as such DNA encodes an amino acid sequence having a transglutaminase activity.

The recombinant DNA of the present invention has one of DNA mentioned above. In this case, the preferred is a DNA having a promoter selected from the group consisting of trp, tac, lac, trc, λ PL and T7.

The transformants of the present invention are obtained by the transformation with the above-mentioned recombinant DNA. Among these, it is preferable that a transformation be conducted by use of a multi-copy vector, and that the transformants belong to Escherichia coli.

The process for producing a protein having a transglutaminase activity according to the present invention comprises the steps of culturing one of the above-mentioned transformants in a medium to produce the protein having a transglutaminase activity and recovering the protein.

The detailed description will be further made on the present invention.

(1) It is known that the expression of MTG in the cells of a microorganism is fatal. It is also known that in the high expression of the protein in a microorganism such as E. coli, the expressed protein is inclined to be in the form of inert insoluble protein inclusion bodies. Under these circumstances, the inventors made investigations for the purpose of obtaining a high expression of MTG as an inert, insoluble protein in E. coli.

A structural gene of MTG used for achieving the high expression is a DNA containing a sequence ranging from thymine base at the fourth position to guanine base at the 993rd position in the base sequence of SEQ ID NO: 2. Taking the degeneration of the genetic codon, the third letter in the degenerate codon in a domain which codes for the N-terminal portion is converted to a codon rich in adenine and uracil and the remaining portion is comprised of a codon frequently used for E. coli in order to inhibit the formation of high-order structure of mRNA, though a DNA which codes for proteins having the same amino acid sequence can have various base sequences.

A strong promoter usually used for the production of foreign proteins is used for the expression of MTG structural gene, and a terminator is inserted into the downstream of MTG structural gene. For example, the promoters are trp, tac, lac, trc, λ PL and T7, and the terminators are trpA, lpp and T4.

For the efficient translation, the variety and number in the SD sequence, and the base composition, sequence and length in the domain between the SD sequence and initiation codon were optimized for the expression of MTG.

The domain ranging from the promoter to the terminator necessitated for the expression of MTG can be produced by a well-known chemical synthesis method. An example of the base sequence is shown in SEQ ID NO: 3. In the amino acid sequence of sequence No. 3, aspartic acid residue follows the initiation codon. However, this aspartic acid residue is preferably removed as will be described below.

The present invention also provides a recombinant DNA usable for the expression of MTG.

The recombinant DNA can be produced by inserting a DNA containing the structural gene of the above-described MTG in a known expression vector selected depending on a desired expression system. The expression vector used herein is preferably a multi-copy vector.

Known expression vectors usable for the production of the recombinant DNA of the present invention include pUC19 and pHSG299. An example of the recombinant DNA of the present invention obtained by integrating DNA of the present invention into pUC19 is pUCTRPMTG-02(+).

The present invention also relates to various transformants obtained by the introduction of the recombinant DNA.

The cells capable of forming the transformant include E. coli and the like.

An example of E. coli is the strain JM109 (recA1, endA1, gyrA96, thi, hsdR17, supE44, relA1,Δ(lac-proAB)/F′ [traD36, proAB+, lacIq, lacZ ΔM15]).

A protein having a transglutaminase activity is produced by culturing the transformant such as that obtained by transforming E. coli JM109 with pUCTRPMTG-02(+) which is a vector of the present invention.

Examples of the medium used for the production include 2xYT medium used in the Example given below and medium usually used for culturing E. coli such as LB medium and M9-Casamino acid medium.

The culture conditions and production-inducing conditions are suitably selected depending on the kinds of the vector, promoter, host and the like. For example, for the production of a recombinant product with trp promoter, a chemical such as 3-β-indoleacrylic acid may be used for efficiently working the promoter. If necessary, glucose, Casamino acid or the like can be added in the course of the culture. Further, a chemical (ampicillin) resistant to genes which are resistant to chemicals kept in plasmid can also be added in order to selectively proliferate a recombinant E. coli.

The protein having a transglutaminase activity, which is produced by the above-described process, is extracted from the cultured strain as follows: After the completion of the culture, the cells are collected and suspended in a buffer solution. After the treatment with lysozyme, freezing/melting, ultrasonic disintegration, etc., the thus-obtained suspension of the disintegrated cells is centrifuged to divide it into a supernatant liquid and precipitates.

The protein having a transglutaminase activity is obtained in the form of a protein inclusion body and contained in the precipitates. This protein is solubilized with a denaturant or the like, the denaturant is removed and the protein is separated and purified. Examples of the denaturants usable for solubilizing the protein inclusion body produced as described above include urea (such as 8M) and guanidine hydrochloride (such as 6 M). After removing the denaturant by the dialysis or the like, the protein having a transglutaminase activity is regenerated. Solutions used for the dialysis are a phosphoric acid buffer solution, tris hydrochloride buffer solution, etc. The denaturant can be removed not only by the dialysis but also dilution, ultrafiltration or the like. The regeneration of the activity is expectable by any of these techniques.

After the regeneration of the activity, the active protein can be separated and purified by a suitable combination of well-known separation and precipitation methods such as salting out, dialysis, ultrafiltration, gel filtration, SDS-polyacrylamide electrophoresis, ion exchange chromatography, affinity chromatography, reversed-phase high-performance liquid chromatography and isoelectric point electrophoresis.

(2) The present invention provides a protein having a transglutaminase activity, which has a sequence ranging from serine residue at the second position to proline residue at the 331st position in the amino acid sequence represented in SEQ ID NO: 1.

The N-terminals of MTG produced by the product transformed with recombinant DNA having a DNA represented in SEQ ID NO: 3 was analyzed to find that most of them contained (formyl)methionine residue of the initiation codon.

However, when a gene which encodes for an exogenous protein is expressed in E. coli, the gene is designed so that the intended protein is positioned after the methionine residue encoded by ATG which is the translation initiation signal for the gene. It is already known that N-terminal methionine residues of a natural protein obtained by the translation from genes are more efficiently cut by methionine aminopeptidase. However, the N-terminal methionine residues are not always cut in the exogenous protein.

It is known that the substrate specificity of methionine aminopeptidase varies depending on the variety of the amino acid residue positioned next to the methionine residue. When the amino acid residue positioned next to the methionine residue is alanine residue, glycine residue, serine residue or the like, the methionine residue is easily cleaved, and when the former is aspartic acid, asparagine, lysine, arginine, leucine or the like, the latter is difficultly cleaved [Nature 326, 315(1987)].

The N-terminal amino acid residue of MTG is aspartic acid residue. When a methionine residue derived from the initiation codon is positioned directly before the aspartic acid residue, methionine aminopeptidase difficultly acts on the obtained sequence, and the N-terminal methionine residue is usually not removed but remains. However, since serine residue is arranged next to N-terminal aspartic acid in MTG, the sequence can be so designed that the amino acid residue positioned next to methionine residue derived from the initiation codon will be serine residue (an amino acid residue on which methionine aminopeptidase easily acts) by deleting aspartic acid residue. Thus, a protein having a high transglutaminase activity, from which the N-terminal methionine residue has been cleaved, can be efficiently produced.

The recombinant protein thus obtained is shorter than natural MTG by one amino acid residue, but the function of this protein is the same as that of the natural MTG. Namely, MTG activity is not lost by the lack of one amino acid. Although there is a possibility that a protein having a transglutaminase activity, from which the methionine residue has not been cleaved, gains a new antigenicity, it is generally understood that the sequence shortened by several residues does not gain a new antigenicity which natural MTG does not have. Thus, there is no problem of the safety.

In fact, a sequence of SEQ ID NO: 62 was designed by deleting N-terminal aspartic acid residue from transglutaminase derived from microorganism (MTG), and this was produced in E. coli. As a result, methionine residue was efficiently removed and thereby there was obtained a protein having a sequence of SEQ ID NO: 62, residues 2-5. It was confirmed that the specific activity of the thus-obtained protein is not different from that of natural MTG.

A process for producing a protein having a transglutaminase activity, which has a sequence ranging from serine residue at the second position to proline residue at the 331st position in the amino acid sequence represented in SEQ ID No. 1 will be described below.

That is, a DNA which encodes for a protein having a transglutaminase activity and having a sequence ranging from serine residue at the second position to proline residue at the 331st position in the amino acid sequence represented in SEQ ID NO: 1 is employed as the MTG structural gene present on recombinant DNA usable for the expression of MTG. Concretely, a DNA having a sequence ranging from thymine base at the fourth position to guanine base at the 993rd position in the base sequence of SEQ ID NO: 2 is employed.

The N-terminal sequence can be altered by an ordinary DNA recombination technique, or specific site directional mutagenesis technique, a technique wherein PCR is used for the whole or partial length of MTG gene, or a technique wherein the part of the sequence to be altered is exchanged with a synthetic DNA fragment by a restriction enzyme treatment.

The transformant thus transformed with the recombinant DNA is cultured in a medium to produce a protein having a transglutaminase activity, and the protein is recovered. The methods for the preparation of the transformant and for the production of the protein are the same as those described above.

Since the protein thus produced has a sequence of Met-Ser- . . . from which the methionine residue is easily cleaved with methionine aminopeptidase, the methionine residue is cleaved in the cell of E. coli to obtain a protein that starts with serine residue.

Although MTG having N-terminal methionine residue is not present in nature, the inventors have found that in some of natural MTG, aspartic acid residue is deleted to have N-terminal serine. Although a protein having N-terminal methionine residue is thus different from natural MTG in the sequence, a protein having N-terminal serine residue is included in the sequences of natural MTG and, in addition, a protein having such a sequence is actually present in the nature. Thus, it can be said that such MTG is equal to natural MTG. Namely, in the production of an enzyme to be used for foods, such as MTG, in which protein antigenicity is a serious problem, it is important to produce a protein having transglutaminase activity and also having a sequence equal to that of natural MTG, or in other words, to produce a sequence from which the N-terminal methionine residue was cleaved.

The following Examples will further illustrate the present invention, which by no means limit the invention.

EXAMPLE Mass Production of MTG in E. coli

<1> Construction of MTG Expression Plasmid pTRPMTG-01

MTG gene has been already completely synthesized, taking the frequency of using codons of E. coli and yeast into consideration (J. P. KOKAI No. Hei 5-199883). However, the gene sequence thereof was not optimum for the expression in E. coli. Namely, all of codons of thirty arginine residues were AGA (minor codons). Under these conditions, about 200 bases from the N-terminal of MTG gene were resynthesized to become a sequence optimum for the expression of E. coli.

As a promoter for transcripting MTG gene, trp promoter capable of easily deriving the transcription in a medium lacking tryptophan was used. Plasmid pTTG2-22 (J. P. KOKAI No. Hei 6-225775) for the high expression of transglutaminase (TG) gene of Pagrus major was obtained with trp promoter. The sequence in the upstream of the TG gene of Pagrus major was designed so that a foreign protein is highly expressed in E. coli.

In the construction of pTRPMTG-01, the DNA fragment from ClaI site in the downstream of trp promoter to BglII site in the downstream of Pagrus major's TG expression plasmid pTTG2-22 (J. P. KOKAI Hei 6-225775) was replaced with the ClaI/HpaI fragment of the synthetic DNA gene and the HpaI/BamHI fragment(small) of pGEM15BTG (J. P. KOKAI Hei 6-30771).

The ClaI/HpaI fragment of the Synthetic DNA gene has a base sequence from ClaI site in the downstream of trp promoter of pTTG2-22 to translation initiation codon, and 216 bases from the N-terminal of MTG gene. The base sequence in MTG structural gene was determined with reference to the frequency of using codon in E coli so as to be optimum for the expression in E. coli. However, for avoiding the high-order structure of mRNA, the third letter of the degenerated codon in the domain of encoding the N-terminal part was converted to a codon rich in adenine and uracil so as to avoid the arrangement of the same bases as far as possible.

The ClaI/Hpal fragment of the Synthetic DNA gene was so designed that it had EcoRI and HindIII sites at the terminal. The designed gene was divided into blocks each comprising about 40 to 50 bases so that the + chain and the − chain overlapped each other. Twelve DNA fragments corresponding to each sequence were synthesized (SEQ ID Nos. 4 to 15). 5′ terminal of the synthetic DNA was phosphatized. Synthetic DNA fragments to be paired therewith were annealed, and they were connected with each other. After the acrylamide gel electrophoresis, the DNA fragments of an intended size was taken out and integrated in EcoRI/HindIII sites of pUC19. The sequence was confirmed and the correct one was named pUCN216. From the pUCN216, a ClaI/HpaI fragment (small) was taken out and used for the construction of pTRPMTG-01.

<2> Construction of MTG Expression Plasmid pTRPMTG-02

Since E. coli JM109 keeping pTRPMTG-01 did not highly express MTG, parts (777 bases) other than the N-terminal altered parts of MTG gene were altered suitably for E. coli. Since it is difficult to synthesize 777 bases at the same time, the sequence was determined, taking the frequency of using codons in E. coli into consideration, and then four blocks (B1, 2, 3 and 4) therefor, each comprising about 200 bases, were synthesized. Each block was designed so that it had EcoRI/HindIII sites at the terminal. The designed gene was divided into blocks of about 40 to 50 bases so that the + chain and the − chain overlapped each other. Ten DNA fragments of the same sequence were synthesized for each block, and thus 40 blocks were synthesized in total (SEQ ID Nos. 16 to 55). 5′ terminal of the synthetic DNA was phosphatized. Synthetic DNA fragments to be paired therewith were annealed, and they were connected with each other. After the acrylamide gel electrophoresis, DNA of an intended size was taken out and integrated in EcoRI/HindIII sites of pUC19. The base sequence of each of them was confirmed and the correct ones were named pUCB1, B2, B3 and B4. As shown in FIG. 2, B1 was connected with B2, and B3 was connected with B4. By replacing a corresponding part of pTRPMTG-01 therewith, pTRPMTG-02 was constructed. The sequence of the high expression MTG gene present on pTRPMTG-02 is shown in SEQ ID No. 3.

<3> Construction of MTG Expression Plasmid pUCTRPMTG-02(+), (−)

Since E. coli JM109 which keeps the pTRPMTG-02 also did not highly express MTG, the plasmid was multi-copied. EcoO109I fragment (small) containing trp promoter of pTRPMTG-02 was smoothened and then integrated into HincII site of pUC19 which is a multi-copy plasmid. pUCTRPMTG-02(+) in which lacZ promoter and trp promoter were in the same direction, and pUCTRPMTG-02(−) in which they were in the opposite direction to each other were constructed.

<4> Expression of MTG

E. coli JM109 transformed with pUCTRPMTG-02(+) and pUC19 was cultured by shaking in 3 ml of 2xYT medium containing 150 μg/ml of ampicillin at 37° C. for ten hours (pre-culture). 0.5 ml of the culture suspension was added to 50 ml of 2xYT medium containing 150 μg/ml of ampicillin, and the shaking culture was conducted at 37° C. for 20 hours.

The cells were collected from the culture suspension and broken by ultrasonic disintegration. The results of SDS-polyacrylamide electrophoresis of the whole fraction, and supernatant and precipitation fractions both obtained by the centrifugation are shown in FIG. 3. The high expression of the protein having a molecular weight equal to that of MTG was recognized in the whole fraction of broken pUCTRPMTG-02(+)/JM109 cells and the precipitate fraction obtained by the centrifugation. It was confirmed by the western blotting that the protein was reactive with mice anti-MTG antibody. The expression of the protein was 500 to 600 mg/L. A sufficient, high expression was obtained even when 3-β-indole acrylic acid was not added to the production medium.

Further, the western blotting was conducted with MTG antibody against mouse to find that MTG was expressed only slightly in the supernatant fraction obtained by the centrifugation and that the expressed MTG was substantially all in the form of insoluble protein inclusion bodies.

<5> Construction of MTG Expression Plasmid pTRPMTG-00

To prove that the change in codon of MTG gene caused a remarkable increase in the expression, pTRPMTG-00 corresponding to pTRPMTG-02 but in which MTG gene was changed to a gene sequence completely synthesized before (J. P. KOKAI No. Hei 6-30771) was constructed.

pTRPMTG-00 was constructed by connecting PvuII/PstI fragment (small) from Pagrus major's TG expression plasmid pTRPMTG-02 with PstI/HindIII fragment (small, including PvuII site) and PvuII/HindIII fragment (small) of pGEM15BTG (J. P. KOKAI No. Hei 6-30771).

<6> Construction of MTG Expression Plasmid pUCTRPMTG-00(+), (−)

pTRPMTG-00 was multi-copied. ECoO109I fragment (small) containing trp promoter and trpA terminator of pTRPMTG-00 was smoothened and then integrated into HincII site of pUC19 which is a multi-copy plasmid. pUCTRPMTG-00(+) in which lacZ promoter and trp promoter were in the same direction, and pUCTRPMTG-00(−) in which they were in the opposite direction to each other were constructed.

<7> Comparison of MTG Expressions

E. coli JM109 transformed with pUCTRPMTG-02 (+) or (−), PUCTRPMTG-00 (+) or (−), pTRPMTG-02, pTRPMTG-01, pTRPMTG-00 or pUC19 was cultured by shaking in 3 ml of 2xYT medium containing 150 μg/ml of ampicillin at 37° C. for ten hours (pre-culture). 0.5 ml of the culture suspension was added to 50 ml of 2xYT medium containing 150 μg/ml of ampicillin, and the shaking culture was conducted at 37° C. for 20 hours.

The cells were collected from the culture suspension, and MTG expression thereof was determined to obtain the results shown in Table 1. It was found that the newly constructed E. coli containing pTRPMTG-00, pUCTRPMTG-00 (+) or (−) did not highly express MTG. This result indicate that it is necessary for the high expression of MTG to change the codon of MTG gene into a codon for E. coli and also to multi-copy the plasmid.

TABLE 1 Strain MTG expression pUCTRPMTG-02(+)/JM109 +++ pUCTRPMTG-02(−)/JM109 +++ pUCTRPMTG-00(+)/JM109 + pUCTRPMTG-00(−)/JM109 + pTRPMTG-02/JM109 + pTRPMTG-01/JM109 + pTRPMTG-00/JM109 − pUC19/JM109 − +++: at least 300 mg/l +: 5 mg/l or below −: no expression

<8> Analysis of N-terminal Amino Acid of Expressed MTG

The N-terminal amino acid residue of the protein inclusion bodies of expressed MTG was analyzed to find that about 60% of the sequence of N-terminal was methionine residue and about 40% thereof was formylmethionine residue. (Formyl)methionine residue corresponding to the initiation codon was removed by a technical idea described below.

<9> Deletion of N-terminal Aspartic Acid Residue of MTG

A base sequence corresponding to aspartic acid residue (the N-terminal of MTG) was deleted by PCR using pUCN216 containing 216 bases as the template. pUCN216 is a plasmid obtained by cloning about 216 bp's containing ClaI-HpaI fragment of N-terminal of MTG in EcoRI/HindIII site of pUC19. pF01 (SEQ ID No. 56) and pR01 (SEQ ID No. 57) are primers each having a sequence in the vector. PDELD (SEQ ID No. 58) is that obtained by deleting a base sequence corresponding to Asp residue. pHd01 (SEQ ID No. 59) is that obtained by replacing C with G not to include HindIII site. pF01 and PDELD are sense primers and pR01 and pHd01 are antisense primers.

35 cycles of PCR of a combination of pF01 and pHd01, and a combination of pELD and pR01 for pUCN216 was conducted at 94° C. for 30 seconds, at 55° C. for one minute and at 72° C. for two minutes. Each PCR product was extracted with phenol/chloroform, precipitated with ethanol and dissolved in 100 μl of H₂O.

1 μl of each of the PCR products was taken, and they were mixed together. After the heat denaturation at 94° C. for 10 minutes, 35 cycles of PCR of a combination of pF01 and pHd01 was conducted at 94° C. for 30 seconds, at 55° C. for one minute and at 72° C. for two minutes.

The second PCR product was extracted with phenol/chloroform, precipitated with ethanol, and treated with HindIII and EcoRI. After pUC19 subcloning, pUCN216D was obtained (FIG. 5). The sequence of the obtained pUCN216D was confirmed to be the intended one.

<10> Construction of the Plasmid Encoding for MTG which Lacks N-terminal Aspartic Acid

Eco0109I/Hpal fragment (small) of pUCN216D was combined with Eco0109I/Hpal fragment (large) of pUCBl-1 (plasmid obtained by cloning HpaII/Bg1II fragment of MTG gene in EcoRI/HindIII site of pUC19) to obtain pUCNB1-2D. Further, ClaI/Bg1II fragment (small) of pUCNB1-2D was combined with ClaI/B/Bg1III fragment (large) of pUCTRPMTG-02(+) which is a plasmid of high MTG expression to obtain pUC TRPMTG(+)D2, the expression plasmid of MTG which lacks N-terminal aspertic acid (FIG. 6). As a result, a plasmid containing MTG gene lacking GAI corresponding to aspartic acid residue as shown in FIG. 7 was obtained.

<11> Expression of the Plasmid Encoding for MTG which Lacks N-terminal Aspartic Acid

E. coli JM109 transformed with pUCTRPMTG(+)D2 was cultured by shaking in 3 ml of 2xYT medium containing 150 μg/ml of ampicillin at 37° C. for ten hours (pre-culture). 0.5 ml of the culture suspension was added to 50 ml of 2xYT medium containing 150 μg/ml of ampicillin, and the shaking culture was conducted at 37° C. for 20 hours. The cells were broken by the ultrasonic disintegration. The results of the dyeing with Coomassie Brilliant Blue dyeing and Western blotting with mouse antiMTG antibody-of the thus obtained supernatant liquid and precipitate indicated that MTG protein lacking N-terminal aspartic acid residue was detected in the precipitate obtained by the ultrasonic disintegration, namely in the insoluble fraction. This fact suggests that MTG protein lacking N-terminal aspartic acid residue was accumulated as protein inclusion bodies in the cells.

The N-terminal amino acid sequence of the protein inclusion bodies was analyzed to find that about 90% thereof was serine as shown in FIG. 8.

The results of the analysis of N-terminal amino acids of expressed MTG obtained in <8> and <11> were compared with each other as shown in Table 2. It was found that by deleting the N-terminal aspartic acid residue from MTG, the initiation methionine added to the N-terminal of the expressed MTG was efficiently removed.

TABLE 2 N-terminal amino acid Strain f-Met Met Asp Ser pUCTRPMTG-02(+)/JM109 40% 60% N.D. pUCTRPMTG(+)D2/JM109 N.D. 10% — 90%

<12> Solubilization of MTG Inclusion Bodies Lacking N-terminal Aspartic Acid Residue, Renaturation of Activity and Determination of Specific Activity

MTG inclusion bodies lacking aspartic acid was partially purified by repeating the centrifugation several times, and then dissolved in 8 M urea [50 mM phosphate buffer (pH 5.5)] to obtain the 2 mg/ml solution. Precipitates were removed from the solution by the centrifugation and the solution was diluted to a concentration of 0.5 M urea with 50 mM phosphate buffer (pH 5.5). The diluted solution was further dialyzed with 50 mM phosphate buffer (pH 5.5) to remove urea. According to Mono S column test, the peak having TG activity was eluted when NaCl concentration was in the range of 100 to 150 mM. The specific activity of the fraction was determined by the hydroxamate method to find that the specific activity of the aspartic acid residue-lacking MTG was about 30 U/mg. This is equal to the specific activity of natural MT G. It is thus apparent that the lack of aspartic acid residue exerts no influence on the specific activity.

62 1 331 PRT Artificial Sequence Description of Artificial SequenceTRANSGLUTAMINASE 1 Asp Ser Asp Asp Arg Val Thr Pro Pro Ala Glu Pro Leu Asp Arg Met 1 5 10 15 Pro Asp Pro Tyr Arg Pro Ser Tyr Gly Arg Ala Glu Thr Val Val Asn 20 25 30 Asn Tyr Ile Arg Lys Trp Gln Gln Val Tyr Ser His Arg Asp Gly Arg 35 40 45 Lys Gln Gln Met Thr Glu Glu Gln Arg Glu Trp Leu Ser Tyr Gly Cys 50 55 60 Val Gly Val Thr Trp Val Asn Ser Gly Gln Tyr Pro Thr Asn Arg Leu 65 70 75 80 Ala Phe Ala Ser Phe Asp Glu Asp Arg Phe Lys Asn Glu Leu Lys Asn 85 90 95 Gly Arg Pro Arg Ser Gly Glu Thr Arg Ala Glu Phe Glu Gly Arg Val 100 105 110 Ala Lys Glu Ser Phe Asp Glu Glu Lys Gly Phe Gln Arg Ala Arg Glu 115 120 125 Val Ala Ser Val Met Asn Arg Ala Leu Glu Asn Ala His Asp Glu Ser 130 135 140 Ala Tyr Leu Asp Asn Leu Lys Lys Glu Leu Ala Asn Gly Asn Asp Ala 145 150 155 160 Leu Arg Asn Glu Asp Ala Arg Ser Pro Phe Tyr Ser Ala Leu Arg Asn 165 170 175 Thr Pro Ser Phe Lys Glu Arg Asn Gly Gly Asn His Asp Pro Ser Arg 180 185 190 Met Lys Ala Val Ile Tyr Ser Lys His Phe Trp Ser Gly Gln Asp Arg 195 200 205 Ser Ser Ser Ala Asp Lys Arg Lys Tyr Gly Asp Pro Asp Ala Phe Arg 210 215 220 Pro Ala Pro Gly Thr Gly Leu Val Asp Met Ser Arg Asp Arg Asn Ile 225 230 235 240 Pro Arg Ser Pro Thr Ser Pro Gly Glu Gly Phe Val Asn Phe Asp Tyr 245 250 255 Gly Trp Phe Gly Ala Gln Thr Glu Ala Asp Ala Asp Lys Thr Val Trp 260 265 270 Thr His Gly Asn His Tyr His Ala Pro Asn Gly Ser Leu Gly Ala Met 275 280 285 His Val Tyr Glu Ser Lys Phe Arg Asn Trp Ser Glu Gly Tyr Ser Asp 290 295 300 Phe Asp Arg Gly Ala Tyr Val Ile Thr Phe Ile Pro Lys Ser Trp Asn 305 310 315 320 Thr Ala Pro Asp Lys Val Lys Gln Gly Trp Pro 325 330 2 993 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 2 gat tct gac gat cgt gtt act cca cca gct gaa cca ctg gat cgt atg 48 Asp Ser Asp Asp Arg Val Thr Pro Pro Ala Glu Pro Leu Asp Arg Met 1 5 10 15 cca gat cca tat cgt cca tct tat ggt cgt gct gaa act gtt gtt aat 96 Pro Asp Pro Tyr Arg Pro Ser Tyr Gly Arg Ala Glu Thr Val Val Asn 20 25 30 aat tat att cgt aaa tgg caa caa gtt tat tct cat cgt gat ggt cgt 144 Asn Tyr Ile Arg Lys Trp Gln Gln Val Tyr Ser His Arg Asp Gly Arg 35 40 45 aaa caa caa atg act gaa gaa caa cgt gaa tgg ctg tct tat ggt tgc 192 Lys Gln Gln Met Thr Glu Glu Gln Arg Glu Trp Leu Ser Tyr Gly Cys 50 55 60 gtt ggt gtt act tgg gtt aac tct ggt cag tat ccg act aac cgt ctg 240 Val Gly Val Thr Trp Val Asn Ser Gly Gln Tyr Pro Thr Asn Arg Leu 65 70 75 80 gca ttc gct tcc ttc gat gaa gat cgt ttc aag aac gaa ctg aag aac 288 Ala Phe Ala Ser Phe Asp Glu Asp Arg Phe Lys Asn Glu Leu Lys Asn 85 90 95 ggt cgt ccg cgt tct ggt gaa act cgt gct gaa ttc gaa ggt cgt gtt 336 Gly Arg Pro Arg Ser Gly Glu Thr Arg Ala Glu Phe Glu Gly Arg Val 100 105 110 gct aag gaa tcc ttc gat gaa gag aaa ggc ttc cag cgt gct cgt gaa 384 Ala Lys Glu Ser Phe Asp Glu Glu Lys Gly Phe Gln Arg Ala Arg Glu 115 120 125 gtt gct tct gtt atg aac cgt gct cta gag aac gct cat gat gaa tct 432 Val Ala Ser Val Met Asn Arg Ala Leu Glu Asn Ala His Asp Glu Ser 130 135 140 gct tac ctg gat aac ctg aag aag gaa ctg gct aac ggt aac gat gct 480 Ala Tyr Leu Asp Asn Leu Lys Lys Glu Leu Ala Asn Gly Asn Asp Ala 145 150 155 160 ctg cgt aac gaa gat gct cgt tct ccg ttc tac tct gct ctg cgt aac 528 Leu Arg Asn Glu Asp Ala Arg Ser Pro Phe Tyr Ser Ala Leu Arg Asn 165 170 175 act ccg tcc ttc aaa gaa cgt aac ggt ggt aac cat gat ccg tct cgt 576 Thr Pro Ser Phe Lys Glu Arg Asn Gly Gly Asn His Asp Pro Ser Arg 180 185 190 atg aaa gct gtt atc tac tct aaa cat ttc tgg tct ggt cag gat aga 624 Met Lys Ala Val Ile Tyr Ser Lys His Phe Trp Ser Gly Gln Asp Arg 195 200 205 tct tct tct gct gat aaa cgt aaa tac ggt gat ccg gat gca ttc cgt 672 Ser Ser Ser Ala Asp Lys Arg Lys Tyr Gly Asp Pro Asp Ala Phe Arg 210 215 220 ccg gct ccg ggt act ggt ctg gta gac atg tct cgt gat cgt aac atc 720 Pro Ala Pro Gly Thr Gly Leu Val Asp Met Ser Arg Asp Arg Asn Ile 225 230 235 240 ccg cgt tct ccg act tct ccg ggt gaa ggc ttc gtt aac ttc gat tac 768 Pro Arg Ser Pro Thr Ser Pro Gly Glu Gly Phe Val Asn Phe Asp Tyr 245 250 255 ggt tgg ttc ggt gct cag act gaa gct gat gct gat aag act gta tgg 816 Gly Trp Phe Gly Ala Gln Thr Glu Ala Asp Ala Asp Lys Thr Val Trp 260 265 270 acc cat ggt aac cat tac cat gct ccg aac ggt tct ctg ggt gct atg 864 Thr His Gly Asn His Tyr His Ala Pro Asn Gly Ser Leu Gly Ala Met 275 280 285 cat gta tac gaa tct aaa ttc cgt aac tgg tct gaa ggt tac tct gac 912 His Val Tyr Glu Ser Lys Phe Arg Asn Trp Ser Glu Gly Tyr Ser Asp 290 295 300 ttc gat cgt ggt gct tac gtt atc acc ttc att ccg aaa tct tgg aac 960 Phe Asp Arg Gly Ala Tyr Val Ile Thr Phe Ile Pro Lys Ser Trp Asn 305 310 315 320 act gct ccg gac aaa gtt aaa cag ggt tgg ccg 993 Thr Ala Pro Asp Lys Val Lys Gln Gly Trp Pro 325 330 3 1519 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 3 ttcccctgtt gacaattaat catcgaacta gttaactagt acgcaagttc acgtaaaaag 60 ggtatcgatt agtaaggagg tttaaa atg gat tct gac gat cgt gtt act cca 113 Met Asp Ser Asp Asp Arg Val Thr Pro 1 5 cca gct gaa cca ctg gat cgt atg cca gat cca tat cgt cca tct tat 161 Pro Ala Glu Pro Leu Asp Arg Met Pro Asp Pro Tyr Arg Pro Ser Tyr 10 15 20 25 ggt cgt gct gaa act gtt gtt aat aat tat att cgt aaa tgg caa caa 209 Gly Arg Ala Glu Thr Val Val Asn Asn Tyr Ile Arg Lys Trp Gln Gln 30 35 40 gtt tat tct cat cgt gat ggt cgt aaa caa caa atg act gaa gaa caa 257 Val Tyr Ser His Arg Asp Gly Arg Lys Gln Gln Met Thr Glu Glu Gln 45 50 55 cgt gaa tgg ctg tct tat ggt tgc gtt ggt gtt act tgg gtt aac tct 305 Arg Glu Trp Leu Ser Tyr Gly Cys Val Gly Val Thr Trp Val Asn Ser 60 65 70 ggt cag tat ccg act aac cgt ctg gca ttc gct tcc ttc gat gaa gat 353 Gly Gln Tyr Pro Thr Asn Arg Leu Ala Phe Ala Ser Phe Asp Glu Asp 75 80 85 cgt ttc aag aac gaa ctg aag aac ggt cgt ccg cgt tct ggt gaa act 401 Arg Phe Lys Asn Glu Leu Lys Asn Gly Arg Pro Arg Ser Gly Glu Thr 90 95 100 105 cgt gct gaa ttc gaa ggt cgt gtt gct aag gaa tcc ttc gat gaa gag 449 Arg Ala Glu Phe Glu Gly Arg Val Ala Lys Glu Ser Phe Asp Glu Glu 110 115 120 aaa ggc ttc cag cgt gct cgt gaa gtt gct tct gtt atg aac cgt gct 497 Lys Gly Phe Gln Arg Ala Arg Glu Val Ala Ser Val Met Asn Arg Ala 125 130 135 cta gag aac gct cat gat gaa tct gct tac ctg gat aac ctg aag aag 545 Leu Glu Asn Ala His Asp Glu Ser Ala Tyr Leu Asp Asn Leu Lys Lys 140 145 150 gaa ctg gct aac ggt aac gat gct ctg cgt aac gaa gat gct cgt tct 593 Glu Leu Ala Asn Gly Asn Asp Ala Leu Arg Asn Glu Asp Ala Arg Ser 155 160 165 ccg ttc tac tct gct ctg cgt aac act ccg tcc ttc aaa gaa cgt aac 641 Pro Phe Tyr Ser Ala Leu Arg Asn Thr Pro Ser Phe Lys Glu Arg Asn 170 175 180 185 ggt ggt aac cat gat ccg tct cgt atg aaa gct gtt atc tac tct aaa 689 Gly Gly Asn His Asp Pro Ser Arg Met Lys Ala Val Ile Tyr Ser Lys 190 195 200 cat ttc tgg tct ggt cag gat aga tct tct tct gct gat aaa cgt aaa 737 His Phe Trp Ser Gly Gln Asp Arg Ser Ser Ser Ala Asp Lys Arg Lys 205 210 215 tac ggt gat ccg gat gca ttc cgt ccg gct ccg ggt act ggt ctg gta 785 Tyr Gly Asp Pro Asp Ala Phe Arg Pro Ala Pro Gly Thr Gly Leu Val 220 225 230 gac atg tct cgt gat cgt aac atc ccg cgt tct ccg act tct ccg ggt 833 Asp Met Ser Arg Asp Arg Asn Ile Pro Arg Ser Pro Thr Ser Pro Gly 235 240 245 gaa ggc ttc gtt aac ttc gat tac ggt tgg ttc ggt gct cag act gaa 881 Glu Gly Phe Val Asn Phe Asp Tyr Gly Trp Phe Gly Ala Gln Thr Glu 250 255 260 265 gct gat gct gat aag act gta tgg acc cat ggt aac cat tac cat gct 929 Ala Asp Ala Asp Lys Thr Val Trp Thr His Gly Asn His Tyr His Ala 270 275 280 ccg aac ggt tct ctg ggt gct atg cat gta tac gaa tct aaa ttc cgt 977 Pro Asn Gly Ser Leu Gly Ala Met His Val Tyr Glu Ser Lys Phe Arg 285 290 295 aac tgg tct gaa ggt tac tct gac ttc gat cgt ggt gct tac gtt atc 1025 Asn Trp Ser Glu Gly Tyr Ser Asp Phe Asp Arg Gly Ala Tyr Val Ile 300 305 310 acc ttc att ccg aaa tct tgg aac act gct ccg gac aaa gtt aaa cag 1073 Thr Phe Ile Pro Lys Ser Trp Asn Thr Ala Pro Asp Lys Val Lys Gln 315 320 325 ggt tgg ccg taatgaaagc ttggatctct aattactgga cttcacacag 1122 Gly Trp Pro 330 actaaaatag acatatctta tattatgtga ttttgtgaca tttcctagat gtgaggtgga 1182 ggtgatgtat aaggtagatg atgatcctct acgccggacg catcgtggcc ggcatcaccg 1242 gcgccacagg tgcggttgct ggcgcctata tcgccgacat caccgatggg gaagatcggg 1302 ctcgccactt cgggctcatg agcgcttgtt tcggcgtggg tatggtggca ggccccgtgg 1362 ccgggggact gttgggcgcc atctccttgc atgcaccatt ccttgcggcg gcggtgctca 1422 acggcctcaa cctactactg ggctgcttcc taatgcagga gtcgcataag ggagagcgtc 1482 gagagcccgc ctaatgagcg ggcttttttt tcagctg 1519 4 39 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 4 aattcatcga ttagtaagga ggtttaaaat ggattctga 39 5 41 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 5 cgatcgtcag aatccatttt aaacctcctt actaatcgat g 41 6 41 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 6 cgatcgtgtt actccaccag ctgaaccact ggatcgtatg c 41 7 41 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 7 gatctggcat acgatccagt ggttcagctg gtggagtaac a 41 8 41 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 8 cagatccata tcgtccatct tatggtcgtg ctgaaactgt t 41 9 41 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 9 attaacaaca gtttcagcac gaccataaga tggacgatat g 41 10 41 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 10 gttaataatt atattcgtaa atggcaacaa gtttattctc a 41 11 41 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 11 tcacgatgag aataaacttg ttgccattta cgaatataat t 41 12 41 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 12 tcgtgatggt cgtaaacaac aaatgactga agaacaacgt g 41 13 41 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 13 gccattcacg ttgttcttca gtcatttgtt gtttacgacc a 41 14 42 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 14 aatggctgtc ttatggttgc gttggtgtta cttgggttaa ca 42 15 40 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 15 agcttgttaa cccaagtaac accaacgcaa ccataagaca 40 16 38 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 16 aattcgttaa ctctggtcag tatccgacta accgtctg 38 17 41 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 17 cgaatgccag acggttagtc ggatactgac cagagttaac g 41 18 49 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 18 gcattcgctt ccttcgatga agatcgtttc aagaacgaac tgaagaacg 49 19 49 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 19 ggacgaccgt tcttcagttc gttcttgaaa cgatcttcat cgaaggaag 49 20 35 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 20 gtcgtccgcg ttctggtgaa actcgtgctg aattc 35 21 35 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 21 gaccttcgaa ttcagcacga gtttcaccag aacgc 35 22 48 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 22 gaaggtcgtg ttgctaagga atccttcgat gaagagaaag gcttccag 48 23 48 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 23 gagcacgctg gaagcctttc tcttcatcga aggattcctt agcaacac 48 24 42 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 24 cgtgctcgtg aagttgcttc tgttatgaac cgtgctctag aa 42 25 39 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 25 agctttctag agcacggttc ataacagaag caacttcac 39 26 45 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 26 aattctctag agaacgctca tgatgaatct gcttacctgg ataac 45 27 50 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 27 cttcttcagg ttatccaggt aagcagattc atcatgagcg ttctctagag 50 28 49 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 28 ctgaagaagg aactggctaa cggtaacgat gctctgcgta acgaagatg 49 29 49 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 29 gagaacgagc atcttcgtta cgcagagcat cgttaccgtt agccagttc 49 30 40 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 30 ctcgttctcc gttctactct gctctgcgta acactccgtc 40 31 39 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 31 ctttgaagga cggagtgtta cgcagagcag agtagaacg 39 32 47 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 32 cttcaaagaa cgtaacggtg gtaaccatga tccgtctcgt atgaaag 47 33 47 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 33 gataacagct ttcatacgag acggatcatg gttaccaccg ttacgtt 47 34 45 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 34 ctgttatcta ctctaaacat ttctggtctg gtcaggatag atcta 45 35 41 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 35 agcttagatc tatcctgacc agaccagaaa tgtttagagt a 41 36 42 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 36 aattcagatc ttcttctgct gataaacgta aatacggtga tc 42 37 44 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 37 catccggatc accgtattta cgtttatcag cagaagaaga tctg 44 38 48 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 38 cggatgcatt ccgtccggct ccgggtactg gtctggtaga catgtctc 48 39 48 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 39 gatcacgaga catgtctacc agaccagtac ccggagccgg acggaatg 48 40 35 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 40 gtgatcgtaa catcccgcgt tctccgactt ctccg 35 41 36 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 41 cttcacccgg agaagtcgga gaacgcggga tgttac 36 42 40 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 42 ggtgaaggct tcgttaactt cgattacggt tggttcggtg 40 43 40 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 43 gtctgagcac cgaaccaacc gtaatcgaag ttaacgaagc 40 44 44 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 44 ctcagactga agctgatgct gataagactg tatggaccca tgga 44 45 41 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 45 agcttccatg ggtccataca gtcttatcag catcagcttc a 41 46 39 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 46 aattcccatg gtaaccatta ccatgctccg aacggttct 39 47 42 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 47 cacccagaga accgttcgga gcatggtaat ggttaccatg gg 42 48 41 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 48 ctgggtgcta tgcatgtata cgaatctaaa ttccgtaact g 41 49 42 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 49 cttcagacca gttacggaat ttagattcgt atacatgcat ag 42 50 37 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 50 gtctgaaggt tactctgact tcgatcgtgg tgcttac 37 51 37 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 51 gtgataacgt aagcaccacg atcgaagtca gagtaac 37 52 38 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 52 gttatcacct tcattccgaa atcttggaac actgctcc 38 53 38 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 53 ctttgtccgg agcagtgttc caagatttcg gaatgaag 38 54 38 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 54 ggacaaagtt aaacagggtt ggccgtaatg aaagctta 38 55 34 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 55 agcttaagct ttcattacgg ccaaccctgt ttaa 34 56 20 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 56 ttttcccagt cacgacgttg 20 57 21 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 57 caggaaacag ctatgaccat g 21 58 36 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 58 taaggaggtt taaaatgtct gacgatcgtg ttactc 36 59 21 DNA Artificial Sequence Description of Artificial SequenceSYNTHETIC DNA 59 tacgccaagg ttgttaaccc a 21 60 5 PRT Artificial Sequence Description of Artificial SequenceN-TERMINAL FRAGMENT 60 Ser Asp Asp Arg Val 1 5 61 15 DNA Artificial Sequence Description of Artificial SequenceCODON FOR N-TERMINAL FRAGMENT 61 tctgacgatc gtgtt 15 62 5 PRT Artificial Sequence Description of Artificial SequenceN-TERMINAL FRAGMENT 62 Met Ser Asp Asp Arg 1 5 

What is claimed is:
 1. A DNA which codes for a protein having transglutaminase activity and comprising an amino acid sequence represented by SEQ ID NO. 1, wherein the base sequence coding for Arg at the fifth position from the N-terminal amino acid is CGT or CGC, and the base sequence coding for Val at the sixth position from the N-terminal amino acid is GTT or GTA.
 2. The DNA of claim 1, wherein the base sequence coding for an amino acid sequence of from the second amino acid to the sixth amino acid from the N-terminal amino acid, (SEQ ID NO: 1, residues 2-6) has the following sequence: Ser: TCT or TCC Asp: GAC or GAT Asp: GAC or GAT Arg: CGT or CGC Val: GTT or GTA.
 3. The DNA of claim 2, wherein the base sequence coding for an amino acid sequence of from the second amino acid to the sixth amino acid from the N-terminal amino acid, (SEQ ID NO: 1, residues 2-6) has the sequence (SEQ ID No: 2, bases 4-18).
 4. The DNA of claim 2, wherein the base sequence coding for an amino acid sequence of from the seventh amino acid to the tenth amino acid from the N-terminal amino acid, (SEQ ID NO: 1, residues 4-7) has the following sequence: Thr: ACT or ACC Pro: CCA or CCG Pro: CCA or CCG Ala: GCT or GCA.
 5. The DNA of claim 3, wherein the base sequence coding for an amino acid sequence of from the seventh amino acid to the tenth amino acid from the N-terminal amino acid, (SEQ ID NO: 1, residues 4-7) has the following sequence: Thr: ACT or ACC Pro: CCA or CCG Pro: CCA or CCG Ala: GCT or GCA. 